6. Source Navigation

6.1. Support for Cross-References

GNAT Studio provides cross-reference navigation for program entities defined in your application such as types, procedures, functions, and variables.

6.3. Highlighting dispatching calls

By default, GNAT Studio highlights dispatching calls in Ada and C++ source code via the dispatching.py plugin. Based on the cross-reference information, this plugin highlights (with a special color you can configure in the preferences dialog) all Ada dispatching calls or calls to virtual methods in C++. A dispatching call in Ada is a subprogram call where the actual subprogram called is not known until run time and is chosen based on the tag of the object.

Disable this highlighting (which may be slow if you have large sources) by using the Edit ‣ Preferences... menu, going to the Plugins section and disabling the dispatching.py plugin.

6.4. Contextual Menus for Source Navigation

This contextual menu is available from any source editor. If you right-click on an entity or selected text, the contextual menu applies to the selection or entity. Most of these menus requires support for cross-references. Here are the main ones regarding navigation.

  • Jump to Specification/Implementation File

    Open the corresponding spec file if the current edited file is a body file, or the body file otherwise. This entry is only available for the Ada language.

  • Go To Declaration

    Go to the declaration (spec) of the clicked entity.

  • Go To Body or Full Declaration

    This entry appears for a private on subprograms or limited private types. Go to body or the full declaration (spec) of the clicked entity.

  • Go To Type Declaration

    Go to the type declaration of the clicked entity.

  • Find All References

    Finds all the references to the clicked entity.

    The option Include overriding and overridden operations includes references to overridden or overriding entities. This is particularly useful if you need to know whether you can easily modify the profile of a primitive operation or method since you can see which other entities would also be changed. If you select only the declaration check box, you see the list of all related primitive operations.

    This dialog allows you to determine which entities are imported from a given file or unit. Click on any entity from that file (for example on the with line for Ada code) and select the All entities imported from same file toggle, which displays in the Location view the list of all entities imported from the same file.

    Selecting the Show context option produces a list of all the references to these entities within the file. If it is not selected, you just get a pointer to the declaration of the imported entities.

  • Call Trees ‣ *Entity* is called by

    Display a list of all subprograms calling the clicked entity in a tree view.

6.5. The gnatinspect cross-reference database (deprecated)

Previous versions of GNAT Studio relied on the compiler for navigation information; this section covers specifics for this engine, which is now deprecated.

6.5.1. The cross-reference database

GNAT Studio parses the cross-reference information generated by the compiler (the .ali) files into one or several sqlite databases (e.g: if your project uses Ada and C). These database files can become quite large and should preferably be on a fast local disk.

By default, GNAT Studio places these database files in the object directory of the currently-loaded root project, or, if specified, in the directory designated by the relative or absolute path given by the Artifacts_Dir attribute of the IDE package of your project file:

--  assume this is in /home/user1/work/default.gpr
project Default is
   for Object_Dir use "obj";

   package IDE is
      for Artifacts_Dir use "artifacts";
      --  All the artifacts generated by GNAT Studio
      --  (including the xref databases)
      --  will be put in the /home/user1/work/artifacts/ directory.
      --
      --  We could also have specified an absolute path here
      --  (e.g: for Artifacts_Dir use "/home/user1/work/artifacts/").
   end IDE;
end Default;

If you want to have more advanced control regarding the naming of the Ada cross-references database file, you can use the Xref_Database in the IDE package of your project file, either as an absolute path or a path relative to the location of the project file. We recommend this path to be specific to each use, and to each project this user might be working on, as in the following examples:

--  assume this is in /home/user1/work/default.gpr
project Default is
   for Object_Dir use "obj";

   package IDE is
      for Xref_Database use "xref_database.db";
      --  This would be /home/user1/work/xref_database.db

      for Xref_Database use Project'Object_Dir & "/xref_database.db";
      --  This would be /home/user1/work/obj/xref_database.db
      --  This is the default when this attribute is not specified

      for Xref_Database use external("HOME") & "/prj1/database.db";
      --  This would be /home/user1/prj1/database.db
   end IDE;
end Default;

One drawback in altering the default location is that gprclean will not remove these database files when you clean your project. But it might speed up GNAT Studio if your project is not on a fast local disk and you can put the databases there.

WARNING: You should not store this file in a directory that is accessed via a network filesystem, like NFS, or Clearcase’s MVFS. If your obj directory is on such a filesystem, be sure to specify a local directory for IDE’Artifacts_Dir project attribute or, if you project only uses Ada, a custom local file path for the IDE’Xref_Database project attribute.

6.5.2. Cross-references and partially compiled projects

The cross-reference engine works best when the cross-reference information generated by the compiler (the .ali files) is fully up to date.

If you start from such a state and then modify the spec or body of an Ada package and recompile only that file, any reference to entities declared in that spec in other packages might no longer be found (until you recompile those other packages, as gprbuild would).

This is because GNAT Studio has no way to know for sure whether an entity Foo in the spec is the same entity as before or is a new one with the same name. It uses an approximate algorithm where the references are only preserved if an entity with the same name remains at precisely the same location in the new version of the source. But if a blank line in the file will change the declaration line for all entities declared further in the file, so those will lose their references from other source files.

6.5.3. Cross-reference and GNAT runtime

By default, GNAT Studio does not parse the GNAT runtime files because there is a large number of them and doing so would significantly slow down GNAT Studio, while producing only a minimal gain for most users. However, the location of subprograms in those runtime files is available from the .ali files corresponding to the sources of your project.

From your own sources, you can navigate to one of the runtime files (for example, if you have a reference to Put_Line(), you will jump to its declaration in a-textio.ads). But you cannot perform cross-reference queries from a runtime file itself.

If you need this capability, enable the preference Project/Cross References in Runtime Files.